Means for elimination of fading on short wave lengths



Jan. 15, 1935.

H. H. BEVERAGE El' AL 1,987,889

MEANS FOR ELIMINATION OF FADiNG ON SHORT WAVE LENGTHS Original Filed Jan. 2, 1926 5 SheetsSheet l F yi Him!

INVENTORS HAROLD H. BEVERAGE Y HAROLD. JET 0N M-u-f/L/ ATTORNEY Jan. 15, 1935. H. H. BEVERAGE ET AL 1,987,339

MEANS FOR ELIMINATION OF FADING ON SHORT WAVE LENGTHS I Original Filed Jan. 2, 1926 3 Sheets-Sheet 2 l l l illlllllik J4 nnnn INVENTORS RARQLD H. BEVERAGE BY HAROLD 0. TERSON ATT'oRNEY Jan. 15, 1935. H. H. BEVERAGE ET AL 1,937,839

MEANS FOR ELIMINATION OF FADING ON SHORT WAVE LENGTHS Original Filed Jan. 2, 1926 I 3 Sheets-Sheet 3 kaz/[rj different 05a mzhrishl's i a g ANT NNHE. 72am?? ell/fare? chamclen'slzbs INVENTORS HRROLD H. BEVERAGE BY HHROLD O.PE EKSDN ATTORN EY or radio signalling.

Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE MEANS FOR ELIMINATION OF FADING ON SHORT WAVE LENGTHS Original application January 2, 1926, Serial No.

Divided and this application January 23, 1930, Serial No. 422,728

8 Claims.

This case is a division of our copending application Serial No. 78,768, filed January 2, 1926.

This invention relates to the elimination of what is commonly known as fading in wireless It is particularly adapted for use in sending and receiving of short waves and in locations where fading is particularly troublesome.

Various theories have been suggested for the explanation of the phenomenon known as fading but it is believed that to date no authentic proven theory has been developed. However, certain evidences and phenomena in connection with fading have been discovered in practical observations. Some of these observations have brought out the fact that short wave signals fade differently at points separated by as little as 500 feet and that the phase relation between these points has been found to reverse several times during a minute. This is, of course, an. extreme case but where the two points are separated at a distance of several miles, this is quite common. For this reason, several methods which have been suggested wherein the phase of the signals coming in at two different points has permanently been adjusted by means of phase correcting devices these systems have been found of little advantage over systems .not using them. The difiiculty has always been that the relative phase or the signal is continually varying, even between nearby points, and fixed phase relations with short wave lengths cannot be obtained by geographical separation, as commonly used on long waves.

Such observations indicate the importance of combining the signals from several receivers in such a manner as to be independent of signal phase in space. For example, if the oscillations from two or more antennae are brought to a common point and combined, the relative phase of the signal oscillations from the different antennae is continually shifting. In two antennae .each may have a strong signal which might periodically swing completely out of phase, resulting in zero signal'at the common point. If theismadeindependentofsignal phase. the signal would always be heard as long as there was any signal voltage induced in either antenna. Several methods already suggested describe a method of combining several antennae at Signal ,frequency .in haphazard fashion. Observations, as indicated above. have shown that haphazard combination is probablynot very efieotlve. whereas combination independent of phase relation is found more effective than might be expected.

There are a great many ways of combining several antennae in such a manner as to be independent of phase relation but no attempt will here be made to describe all of them which should be obvious to one skilled in the art. Only a few of the more preferred forms will be explained.

Referring particularly to the drawings, Fig. 1 shows a simple method of haphazard combination. This method is rather ineffective because of thesignal phase continually shifting between the various antennae.

Fig. 2 shows another method for combining the oscillations independent of phase relation and is considerably more effective than .the method shown in Fig. 1.

Figs. 3 to 5 inclusive and 7 show other methods of obtaining this combination independent of phase relation.

Fig. 6 shows an arrangement utilizing the method of phase reversal at both sending and receiving stations. These phase reversals may be operated synchronously or not, as desired. Various combinations and detailed methods of operation might be possible with this arrangement.

Further and more definite objects and advantages of the use of this system will appear in connection with the figures of the drawings in the following specification and clalms:-

1 and 2 of Fig. 1 show two antenna: coupled to the transmission lines 3 and 4 to a single coupling coil with connections at 5 to either a sending or a receiving apparatus. ment while advantageous for some purposes, does not entirely prevent fading, because two signal oscillation trains may be received on both antennae at the same time but may be degrees out of phase from each other in such. a way as to entirely neutralize in any receiving apparatus connected at 5. The same would be true of any sending apparatus but with opposite effect.

6 and 7 of Fig. 2 are geographically separated antennae coupled to transmission systems to which is coupled local heterodyne oscillators 8 and 9. The reotifiers 10 and 11 transmit a beat frequency through the uniting transformer 12 which is connected to the phones 13. It can be seenfrom this that the audiofrequencies are combined after detection and are determined by the audiofrequency phase relation caused. by both signal and oscillator phase. since the This arrangeequal average signal intensities.

oscillators are separate, the audio frequencies may be and preferably are made different and each audio frequency exists independently as long as signal energy is coming in on that particular antenna irrespective of phase. When several antenna are combined in this manner, the character of the composite tone changes as fading occurs in the individual receivers, but the tone never disappears entirely unless the signal is zero at all the receivers simultaneously. A practical limit in the number of receivers is soon reached when it is necessary to rectify the composite audiofrequency. .This rectification thereby brings out the beats between components so it is essential to separate the audiofrequencies far enough to give several cycles of the lowest beat note per dot of si nalling frequency.

For example, assuming the circuit is operated at 100 words per minute. a dot frequency .of 40 cycles per second. It would therefore ,be necessary to separate the audiofrequencies 200 cycles to give 5 cycles to a dot. 'This would limit the practical number of antenna: to.6' or Bat the most.

14 and 15 of Fig. 3 also show antennae separated by' an appreciable distance and whose output circuits are coupled to a single lieterodyne oscillator '16,and connected to rectifiers l7 and 18 and to amplifiers l9 and 20 respectively. 21 is a' signal recorder of a well known type for recording'a signal which afiect the antenna, and vacuum tubes, 23 are arranged for the purpose of rectifying the different signals as they affect the two circuits connected to the recorder. It can be seen from this that voltages produced rr mqne antenna will affect. one circuit, while those produced on the other antenna afiect the other circuit and since recorder 21 is in both 'circuits'it will always be operated as long as the signal exists "in either. With this arrangement any number of rectifiers may be connected in ,parallel and any number of antennae used.

Making the'reference to, Fig. 4,. 24 and 25 in- 'coil 29. coupling. The other end of this combining coil coupling is connected to a vibrator 27 which contacts withthe outer ends of the double -coil;26i This-vibrator is operated by an oscillatingcircuit- 28 and maybe operated at 60 cycles or' more; This arrangement has p'roven the most preferable.

If more antenna are used, they should be connectedthrough similar or the same apparatus as is 'used with antenna 25 so that only one "antenna is directly connected to the combining coil.

In the operation of this arrangement, the couplings to theantenna are adjusted to give If the intensities from the two antennae remain about the sarne no changevwill result from a phase relation difierence of 180 degrees or any other phase relation/because the output of one antenna is reversed "several times per signal dot or dash as the case may be, making the average result independent of phase, It the signal fades on one antenna, it will s' till be heard on the other antenna. 'I he'sig'nal from the reversed antenna sounds" almdst the same {whether the reversing This corresponds to is that the relay introduces side bands which result in a slight change in the character of the signal.

This same principle may be applied to any number of antennae, each antennahavinga separate' reversing device. Anyinunrber of signals can be received from the same antenna: and each signal will receive the benefit of the fading elimination.

The modification shown in Fig. 5 discloses a pushpull coupling tube arrangement which would be reversed by a local oscillator. 30 and 31 are diagrammatic showings of antennae separated apart. Antenna 30 is coupled through a transmission line directly to the combining coils 34. Antenna 31 is coupled to the push-pull amplifier through coils 52 and 53 which is controlled by a local oscillator 33 at 32 to reverse the direction of oscillation in respect to the com bining coils 34. Where a high frequency of reversal is obtained, there arises a disadvantage of producing side bands on other signals which. might interfere but this" can be eliminated by any known means such as filters or tuned circuits, etc. By using a super-audible frequency for reversal, this device may be applied to telephony for eliminating fading and other distortion. If more antennae were used, they should be con nected' through the pushpull coupling tubearrangement as shown in connection with antenna There is alsoi evidence derived from observations that antennae having diiferent directional characteristics but located at or near the same place showentirely diiferent degrees of fading. For example, it might be advantageous to combine a horizontalloop with a vertical loop; a wave antenna with a vertical antenna, etc. For short waves the vertical directive diagram is of importance as well as the horizontal directive diagram arrangen'i'entf Thus, instead of connecting ordinary types of antenna as shown in the various figures; any one of theother known types of directive or distorting antenna might be used in any combination desirable. This type of combination is dependent upon the natural characteristics ofthe surroundings and no general law has been disooveredwhich would apply .in all cases. The best arrangement can only be determined by experimentation "at a particular place. While it is probably easier and cheaper to applythe de phasing'principle at the receiver, there is noreason why the same principle could not be applied at the transmitter; "A common transmitter could be used to feed two or more spaced. ntenna, each having a separate phase reversal device." v

Such an arrangement is shown in Fig; 6 where 35 is as'our'ce of radio frequency oscillations modulated by'ithe key or other device 51 and coupled directly to the antenna 37; but through a vibrator 49 to the antenna-'39." The vibrator 40 is operated by a' local source of oscillations 38, 'I'l e oscillations produced by the sending arrangement could be received by a device such as is shown in Fig. 4 or any other of the disclosures. Thus, if antennae 41" and 42 were coupled to a common output coil 46', the additional advantage of preventing fading and phase reversal at the receiving end as well asthe transmitting end would be obtained. 43 would be the coupling coil to the combining coil 46' for antenna 41 while the coupling from antenna e2-would'be made to the vibrating reverse?' lififi iatedbythe' source of oscillatlbns 45. From the figure, it can be seen that four diflerent paths might be taken by the oscillations as indicated at 47, 48, 49 and 50, thus assuring continuous transmission.

Another variation of the connections of Fig. is shown in Fig. 7. Here 54 and 55 are the antenna with impedance coils connected to ground. 54 is directly coupled to the output coupling. The antenna 55 is capacitatively coupled at 57 and 58 to the pushpull tube arrangement 59. Here resistance elements 60 and 61 are connected to balanced coupling coils 62 and 63, coupled to oscillator 64. By-pass condensers 65 and 66 allow the oscillatory current to pass around the circuit which they are in and tend to keep the two ends of coils 62 and 63 at the same instantaneous potential. The customary A, B and C batteries are shown at 67, 68 and 69 respectively. The output coils are shown at 70 coupled to coil 71. Thus the two outputs of antenna 54 and 55 appear at the circuit 56 and '70.

If an oscillation is now impressed equally on the two antenna reversal of the oscillator 64 will first block the transmission through one tube and then the other. In this way first one output coil at '70 will be energized and then the other according to the rate of oscillation. The oscillations may be at an audible or asuperaudible rate.

Also it is obvious that antenna having different directive characteristics located at the same point might as well be used as two nondirectional antenna at different points. Such antenna might be of the kind indicated at 54 and 55 of Fig. 7.

The type of phase reversal devices might as well be rotating contact devices, rotating capacity couplers, time lag devices of different values, such as an artificial line for successively! controlling the grids of coupling tubes associated with the several antenna, etc.

It is not intended to be limited to the exact modification shown, but any of the modifications above described might as well be used within the scope of the following claims:

We claim:

1. In a radio signaling system, the combination of a short wave carrier generator, an antenna, means for feeding carrier waves generated 'by said generator to said antenna, means for turning on and off the waves fed into said antenna, a generator of non-intelligence bearing audiofrequency waves, and means for continuously changing the phase of the waves fed into said antenna in accordance with said audiotrequency waves whereby fading of signals received from said antenna is substantially reduced.

2. In a signaling system the combination of a plurality of antenna, a carrier generator, means to vary the carrier generated in accordance with intelligence to be transmitted, means for feeding the modulated carrier to all of said antenna, means for generating a non-intelligence bearing audio-frequency wave, and means for varying the phase of the modulated carrier fed to one of said antenna in accordance with said non-intelligence bearing audio-frequency wave whereby fading of the radiated energy is substantially reduced.

3. In a radio signaling system for the reduction of fading, a plurality of spaced antenna a plurality of which have different directional characteristics, a carrier generator, means to modulate the carrier, means for energizing the antenna with modulated carrier energy, and means for changing the relative phase of carrier energy supplied to one of the antenna.

4. In a radio signaling system, the combination of a generator of carrier waves, an antenna, means for feeding carrier waves generated by said generator into said antenna, means for keying the waves fed into said antenna, a source of non-intelligence bearing audiofrequency waves, and means for varying the phase of the waves fed into said antenna in accordance with said non-intelligence bearing waves whereby the effective fading of signals at a receiver received from said antenna is substantially minimized.

5. In a radio signaling system for the'reduction of fading, a plurality of spaced antenna a plurality of which have different directional characteristics, a carrier generator, means to modulate the carrier, means for energizing the antenna with modulated carrier energy and means for continuously changing the relative phase of carrier energy supplied to one of the antenna; and, a receiver comprising means for effectively continuously relatively changing the phase of the received carrier.

6. In a system for reducing short wave fading, a carrier wave generator, an antenna, means for feeding the waves from said generator into said antenna, a sourceof non-intelligence bearing waves, and means for reversing the phase of said carrier waves fed into said antenna in accordance with waves from said non-intelligence bearing source.

7. In combination, a carrier generator, a pair of antenna, means for modulating the carrier generated, means for feeding the modulated carrier into each of said antenna, a source of nonintelligence bearing waves, and means for varying the phase of the modulated carrier fed into one of said antenna in accordance with waves from said non-intelligence bearing source, whereby fading of the carrier at a receiver is substantially reduced.

8. In a signaling system, a plurality of antenna, a generator of carrier waves, means for keying said carrier waves, means for feeding said keyed carrier waves to all of said antenna whereby all of said antenna radiate said-keyed carrier waves, and means associated with one of said feeding means for continuously varying the phase of keyed carrier waves fed to one of said antenna.

HAROLD H. BEVERAGE. HAROLD O. PETERSON. 

